Event detection in an implantable auditory prosthesis

ABSTRACT

Presented herein are techniques for monitoring the physical state of a stimulating assembly to, for example, detect the occurrence of an adverse event. More specifically, an elongate stimulating assembly comprising a plurality of longitudinally spaced contacts is at least partially implanted into a recipient. Electrical measurements are performed at one or more of the plurality of contacts and the electrical measurements are evaluated relative to one another to determine the physical state of the stimulating assembly.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation application of U.S. patentapplication Ser. No. 15/679,644, entitled “Event Detection In AnImplantable Auditory Prosthesis,” filed on Aug. 17, 2017, which is acontinuation application of U.S. patent application Ser. No. 14/843,255,entitled “Event Detection In An Implantable Auditory Prosthesis,” filedon Sep. 2, 2015, which in turn claims priority to U.S. ProvisionalApplication No. 62/044,595, entitled “Event Detection in an ImplantableAuditory Prosthesis,” filed Sep. 2, 2014. The content of theseapplications are hereby incorporated by reference herein.

BACKGROUND Field of the Invention Related Art

Hearing loss, which may be due to many different causes, is generally oftwo types, conductive and/or sensorineural. Conductive hearing lossoccurs when the normal mechanical pathways of the outer and/or middleear are impeded, for example, by damage to the ossicular chain or earcanal. Sensorineural hearing loss occurs when there is damage to theinner ear, or to the nerve pathways from the inner ear to the brain.

Individuals who suffer from conductive hearing loss typically have someform of residual hearing because the hair cells in the cochlea areundamaged. As such, individuals suffering from conductive hearing losstypically receive an auditory prosthesis that generates motion of thecochlea fluid. Such auditory prostheses include, for example, acoustichearing aids, bone conduction devices, and direct acoustic stimulators.

In many people who are profoundly deaf, however, the reason for theirdeafness is sensorineural hearing loss. Those suffering from some formsof sensorineural hearing loss are unable to derive suitable benefit fromauditory prostheses that generate mechanical motion of the cochleafluid. Such individuals can benefit from implantable auditory prosthesesthat stimulate nerve cells of the recipient's auditory system in otherways (e.g., electrical, optical and the like). Cochlear implants areoften proposed when the sensorineural hearing loss is due to the absenceor destruction of the cochlea hair cells, which transduce acousticsignals into nerve impulses. Auditory brainstem stimulators might alsobe proposed when a recipient experiences sensorineural hearing loss dueto damage to the auditory nerve.

SUMMARY

In one aspect of the invention, a system is provided. The systemcomprises an elongate stimulating assembly configured to be implanted ina recipient, wherein the stimulating assembly comprises a plurality oflongitudinally spaced contacts, and an event detection processorconfigured to utilize variations in electrical measurements between twoor more contacts to determine a physical state of the stimulatingassembly.

In another aspect of the invention, a method for monitoring animplantable stimulating assembly comprising a plurality oflongitudinally spaced contacts is provided. The method comprisesdelivering electrical stimulation between two or more of the contacts,measuring electrical parameters at a selected number of the plurality ofcontacts in response to the delivered electrical stimulation, andevaluating the measured electrical parameters relative to one another todetermine a physical state of the stimulating assembly.

In another aspect of the invention, one or more non-transitory computerreadable storage devices encoded with software comprising computerexecutable instructions for monitoring an implantable stimulatingassembly comprising a plurality of longitudinally spaced contacts areprovided. When the software is executed, the software is operable todeliver electrical stimulation between two or more of the contacts,measure electrical parameters at a selected number of the plurality ofcontacts in response to the delivered electrical stimulation, andevaluate the measured electrical parameters relative to one another todetermine a physical state of the stimulating assembly.

In another aspect of the invention, a cochlear implant system isprovided. The cochlear implant system comprises an intra-cochlearstimulating assembly comprising a plurality of contacts and configuredto deliver electrical stimulation between two or more of contacts, animplantable stimulator unit, and a processor. The processor isconfigured to measure, via the implantable stimulator unit, electricalparameters at a selected number of the plurality of contacts in responseto the delivered electrical stimulation, and evaluate the measuredelectrical parameters relative to one another to determine a physicalstate of the stimulating assembly.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the present invention are described herein in conjunctionwith the accompanying drawings, in which:

FIG. 1 is a schematic diagram of a cochlear implant in accordance withembodiments presented herein;

FIG. 2A is schematic diagram of a stimulating assembly during normalinsertion into a recipient's cochlea;

FIG. 2B is a schematic diagram illustrating an adverse event that mayoccur during insertion of a stimulating assembly into a recipient'scochlea;

FIG. 2C is a schematic diagram illustrating another adverse event thatmay occur during insertion of a stimulating assembly into a recipient'scochlea;

FIG. 3 is a flowchart of a localized monitoring method in accordancewith embodiments presented herein;

FIG. 4A is a graph illustrating electrical measurements obtained throughthe localized monitoring method of FIG. 3 during a normal insertion;

FIG. 4B is a graph illustrating electrical measurements obtained throughthe localized monitoring method of FIG. 3 during an insertion in whichtip foldover occurs;

FIG. 4C is a graph illustrating electrical measurements obtained throughthe localized monitoring method of FIG. 3 during an insertion in whichdeformation occurs;

FIG. 5 is a flowchart of a bipolar monitoring method in accordance withembodiments presented herein;

FIG. 6A is a graph illustrating electrical measurements obtained throughthe bipolar monitoring method of FIG. 5 during a normal insertion;

FIG. 6B is a graph illustrating electrical measurements obtained throughthe bipolar monitoring method of FIG. 5 during an insertion in which tipfoldover occurs;

FIG. 6C is a graph illustrating electrical measurements obtained throughthe bipolar monitoring method of FIG. 5 during an insertion in whichdeformation occurs;

FIG. 7 is a block diagram of a cochlear implant configured to performmonitoring techniques in accordance with embodiments presented herein;

FIG. 8 is a block diagram of a processing configured to performmonitoring techniques in accordance with embodiments presented herein;and

FIG. 9 is a flowchart of a method in accordance with embodimentspresented herein.

DETAILED DESCRIPTION

Presented herein are techniques for monitoring the physical state of astimulating assembly to, for example, detect the occurrence of anadverse event. More specifically, an elongate stimulating assemblycomprising a plurality of longitudinally spaced contacts is at leastpartially implanted into a recipient. Electrical measurements areperformed at one or more of the plurality of contacts and the electricalmeasurements are evaluated relative to one another to determine thephysical state of the stimulating assembly.

There are different types of auditory prostheses that may be partiallyor fully implanted into a recipient, including electrically stimulatingauditory prostheses such as cochlear implants and auditory brainstemstimulators. It is to be appreciated that monitoring techniquespresented herein may be used in connection with any of the above orother implantable auditory prostheses. However, merely for ease ofdescription, embodiments of the present invention are primarilydescribed herein with reference to a cochlear implant.

FIG. 1 is perspective view of an exemplary cochlear implant 100 inaccordance with embodiments presented herein. The cochlear implant 100includes an external component 102 and an internal/implantable component104. The external component 102 is directly or indirectly attached tothe body of the recipient and typically comprises an external coil 106and, generally, a magnet (not shown in FIG. 1) fixed relative to theexternal coil 106. The external component 102 also comprises one or moresound input elements 108 (e.g., microphones, telecoils, etc.) fordetecting sound and a sound processing unit 112. The sound processingunit 112 may include, for example, a power source (not shown in FIG. 1)and a sound processor (also not shown in FIG. 1). The sound processor isconfigured to process electrical signals generated by a sound inputelement 108 that is positioned, in the depicted embodiment, by auricle110 of the recipient. The sound processor provides the processed signalsto external coil 106 via a cable (not shown in FIG. 1).

The implantable component 104 comprises an implant body 114, a leadregion 116, and an elongate intra-cochlear stimulating assembly 118. Theimplant body 114 comprises a stimulator unit 120, aninternal/implantable coil 122, and an internal receiver/transceiver unit124, sometimes referred to herein as transceiver unit 124. Thetransceiver unit 124 is connected to the internal coil 122 and,generally, a magnet (not shown) fixed relative to the internal coil 122.

The magnets in the external component 102 and implantable component 104facilitate the operational alignment of the external coil 106 with theinternal coil 122. The operational alignment of the coils enables theimplantable coil 122 to transmit/receive power and data to/from theexternal coil 106. More specifically, in certain examples, external coil106 transmits electrical signals (e.g., power and stimulation data) toimplantable coil 122 via a radio frequency (RF) link. Implantable coil122 is typically a wire antenna coil comprised of multiple turns ofelectrically insulated single-strand or multi-strand platinum or goldwire. The electrical insulation of implantable coil 122 is provided by aflexible molding (e.g., silicone molding). In use, transceiver unit 124may be positioned in a recess of the temporal bone of the recipient.Various other types of energy transfer, such as infrared (IR),electromagnetic, capacitive and inductive transfer, may be used totransfer the power and/or data from an external device to cochlearimplant and FIG. 1 illustrates only one example arrangement.

Elongate stimulating assembly 118 is configured to be at least partiallyimplanted in cochlea 130 and includes a plurality of intra-cochlearcontacts 128. The contacts 128 collectively form a contact array 126 andmay comprise electrical contacts and/or optical contacts.

Stimulating assembly 118 extends through an opening in the cochlea 130(e.g., cochleostomy 132, the round window 134, etc.) and has a proximalend connected to stimulator unit 120 via lead region 116 that extendsthrough mastoid bone 119. Lead region 116 couples the stimulatingassembly 118 to implant body 114 and, more particularly, stimulator unit120.

An intra-cochlear stimulating assembly, such as stimulating assembly118, may be a perimodiolar stimulating assembly or a non-perimodiolarstimulating assembly. A perimodiolar stimulating assembly is astimulating assembly that is configured to adopt a curved configurationduring and/or after implantation into the recipient's cochlea so as tohave a distal section positioned close to the wall of the recipient'smodiolus (i.e., close to the modiolar wall). The modiolus is a conicalshaped central region in the cochlea around which the cochlea canals(i.e., scala tympani, scala media, and scala vestibule) spiral. Themodiolus consists of spongy bone in which the cochlea nerve cells,sometimes referred to herein as the spiral ganglion cells, are situated.The cochlea canals generally turn 2.5 times around the modiolus.

In general, the sound processor in sound processing unit 112 isconfigured to execute sound processing and coding to convert a detectedsound into a coded signal corresponding to electrical signals fordelivery to the recipient. The coded signal generated by the soundprocessor is then sent to the stimulator unit 120 via the RF linkbetween the external coil 106 and the internal coil 122. The stimulatorunit 120 includes one or more circuits that use the coded signals,received via the transceiver unit 124, so as to output a series ofelectrical stimulation signals (stimulation current) via one or morestimulation channels that terminate in the intra-cochlear stimulatingcontacts 128. As such, the stimulation current is delivered to therecipient via the intra-cochlear stimulating contacts 128. In this way,cochlear implant 100 stimulates the recipient's auditory nerve cells,bypassing absent or defective hair cells that normally transduceacoustic vibrations into neural activity.

To insert an intra-cochlear stimulating assembly 118 into a recipient,an opening (facial recess) is created through the recipient's mastoidbone 119 to access the recipient's middle ear cavity 141. The surgeoncreates an opening from the middle ear into the cochlea 130 through, forexample, the round window, oval window, the promontory, etc. of thecochlea 130. The surgeon then gently pushes the stimulating assembly 118forward into the cochlea 130 until the stimulating assembly 118 achievesa desired position.

In conventional intra-cochlear stimulating assembly insertiontechniques, the surgeon operates “blind.” That is, due to the nature ofthe access (through the facial recess and the middle ear cavity), thesurgeon cannot actually see the stimulating assembly 118 once it passesinto the cochlea 130. Therefore, the surgeon relies upon only touch/feelduring the insertion.

Most stimulating assembly insertions occur without incident, which isattributed to the design of the stimulating assembly, surgicalguidelines, and surgeon skill. However, there are occasions when eventsoccur during stimulating assembly insertion which can be called“adverse” in that the event may cause increased trauma to the cochlea,and/or negatively impact the performance or placement of the stimulatingassembly.

FIG. 2A illustrates stimulating assembly 118 during a normal (good)insertion into a recipient's cochlea 130 (i.e., an insertion where noadverse events occur). FIGS. 2B and 2C illustrate several adverse eventsthat may occur during insertion of the stimulating assembly 118 into therecipient's cochlea 130.

The stimulating assembly 118 comprises a carrier member 244 formed froma resiliently flexible material, such as silicone. A plurality of spacedcontacts 128 are mounted or disposed in/on at least a first surface 246of the carrier member 244 and collectively form a contact array 126. Itshould be appreciated that as used herein, particular combinations ofthe terms mounted/disposed, in/on, etc., are not to be interpreted torefer to any particular manufacturing technique or structuralrelationship.

In the specific examples of FIGS. 2A-2C, the stimulating assembly 118includes twenty-two (22) intra-cochlear contacts. For ease of reference,the contacts 128 are numbered sequentially as contacts 128(1)-128(22)such that contact 128(1) is the most proximal contact (i.e., the contactdisposed at the proximal end of the contact array 126) and contact128(22) is the most distal contact (i.e., the contact disposed at thedistal end/tip 236 of the contact array 126). It is to be appreciatedthat the number of contacts shown in FIGS. 2A-2C is merely illustrativeand different numbers of contacts may be present in other embodiments.

As noted above, FIG. 2A illustrates a normal insertion where thestimulating assembly 118 travels smoothly through the cochlea canal(e.g., the scala tympani) 250. That is, as the surgeon inserts thestimulating assembly 118, the distal end 236 (i.e., the most apical endof distal region 237) travels towards the cochlea apex 252 without theoccurrence of any adverse events. In contrast, FIG. 2B illustrates anexample where obstacles, friction and/or other forces cause the distalend 236 of the stimulating assembly 118 to stick to (i.e., get caughton) a wall, such as inner wall 238, of the cochlea 130 instead oftravelling smoothly down the length of the cochlea. In this example, notonly can the surgeon not see that the distal end 236 is caught on theinner wall 238, but he/she also may not feel the resistance provided bythe wall. As such, the surgeon may continue to push the stimulatingassembly 118 into the cochlea 130 and the stimulating assembly may foldover onto itself. This type of event is generally referred to as tipfoldover and could cause damage to the soft tissue structures within thecochlea, resulting in trauma and potential loss of residual hearing.Additionally, the contacts of stimulating assembly 118 within the“folded” region (e.g., 128(22)-128(18) in FIG. 2B) may become unusable,reducing the benefit of the cochlear implant 100 for the recipient.

In a further example shown in FIG. 2C, the stimulating assembly 118deforms or buckles at a point along the length of the stimulatingassembly, shown as region 240. Deformation may occur, for example, whenthe distal end 236 of the stimulating assembly 118 catches onto astructure inside the cochlea 130 within its insertion path. Deformation,which cannot be seen by the surgeon, may result in damage to the softtissue structures. Additionally, the contacts of stimulating assembly118 within the “deformed” region (e.g., contacts 128(14)-128(8) in FIG.2C) may also become unusable, resulting in a reduction in hearingperformance for the recipient. Deformation may also prevent thestimulating assembly 118 from assuming an optimal placement, such as aposition close to the modiolus 242.

As noted above, these adverse events may detract from the benefit of thecochlear implant to the recipient, namely by increasing trauma anddecreasing performance. Most surgeons use post-operative X-rays to checkfor the occurrence of these adverse events. Since these X-rays are takenafter the wound is closed, the correction of adverse events requires thesurgeon to re-open the wound. Presently, there are no techniques thatprovide a surgeon with real-time information about the physical state ofthe stimulating assembly in the cochlea. Instead, as noted, evidence ofan adverse event only becomes available to the surgeon if post-operativechecks are performed.

Presented herein are techniques for real-time (e.g., intraoperative)monitoring of the physical state of an implantable stimulating assemblyin order to provide real-time feedback on the occurrence of adverseevents within the cochlea, thereby assisting surgeons in obtainingimmediate information about the quality of the stimulating assemblyinsertion. The physical state of the stimulating assembly refers to theshape/configuration of the stimulating assembly within the recipient'scochlea, brainstem, etc. In general, the physical state monitoringtechniques presented herein use variations in measured electricalparameters (electrical data), such as voltages and impedances, takenfrom various locations along a contact array to provide an indication ofthe physical state of the stimulating assembly and, as such, whether anyadverse events have occurred during insertion.

Evidence of adverse events such as tip foldover and deformation/bucklingcan be derived from information about the location of stimulatingassembly contacts relative to one another within the space of thecochlea. That is, the incorrect positioning and/or obstruction of thestimulating assembly caused by an adverse event may bring certainstimulating assembly contacts closer to one another than would normallyoccur in a normal (good) insertion. The unexpected close proximity ofcertain contacts results in changes in the direction of the electricfield, leading to electrical measurements recorded at the stimulatingassembly contacts that are distinct from those of a normal insertion.Such differences in electrical field direction are exploited by theproposed method for the purpose of detecting the occurrence of adverseevents.

The electrical information can be obtained by delivering stimulation(i.e., current signals) from at least one point along the contact arrayand then recording electrical parameters (e.g., voltage or impedance)from at least one other point along the same contact array. Thesemeasurements can be performed in real-time, such that electrical data isobtained continuously throughout the insertion. Simple post-processingof the recorded data is only required for generating a plot of theelectrical measurements.

The proposed techniques do not rely on the specific values of themeasured data to determine whether an adverse event has occurred.Instead, the relative magnitudes of the recorded values and the shapesof the plots they generate are used for the determination. The data isanalyzed for key characteristics and trends which indicate whether theinsertion outcome is normal/expected or if any adverse events haveoccurred

The techniques presented herein include several methods for monitoringthe physical state of a stimulating assembly in order to, for example,detect the occurrence of adverse events during insertion of astimulating assembly. The monitoring methods presented herein candemonstrate the physical state of the stimulating assembly using onesingle set of data points, namely one set of measurement data recordedfor a selected number of contacts within the contact array in responseto a single stimulation pattern. As described further below, the singlestimulation pattern may refer to the delivery of localized currentsignals (with a subsequent measurement at each of a selected number ofcontacts) or the sequential delivery of bipolar current signals betweena first contact and each of the selected number of contacts (with asubsequent measurement at each of the selected number of contacts). Asdescribed further below, the monitoring methods described herein mayutilize various interfaces for initiating and controlling the electricalmeasurements using a cochlear implant, auditory brainstem implant, etc.

FIG. 3 is a flowchart of a first method 300 for monitoring the physicalstate of the stimulating assembly through the use of localizedstimulation. The method 300 of FIG. 3 is sometimes referred to herein asa localized monitoring method as the method uses the delivery oflocalized stimulation (i.e., current signals) to induce voltages at aplurality of other contacts. For ease of illustration, method 300 willbe described with reference to the cochlear implant 100 of FIG. 1 anddetails of stimulating assembly 118 shown in FIGS. 2A-2C.

Method 300 begins at 302 where stimulation (i.e., one or more currentsignals) is delivered/sourced at a selected intra-cochlear contact. Inone specific example, the stimulation is delivered at the mostdistal/apical contact 128(22) and is sunk at the second most distalcontact 128(21) (i.e., the contact adjacent to contact 128(22)). Thecontact that delivers the current signals, namely contact 128(22), issometimes referred to herein as the “stimulating” or “source” contactand the contact that sinks the current signals, namely contact 128(21),is sometimes referred to herein as the “return” contact. Additionally,the two contacts between which the stimulation is delivered (i.e., themost distal/apical contacts in the embodiment of FIG. 3) arecollectively referred to herein as a “stimulating pair.” The remainingcontacts that are not part of the stimulating pair are disconnected fromthe system ground (i.e., are electrically “floating”).

In general, two intra-cochlear contacts are selected for delivery of thestimulation. However, alternative embodiments may use an extra-cochlearcontact to source/sink current. Additionally, it is to be that the useof the most distal contacts for sourcing/sinking the current isillustrative and other contacts could be used in alternativeembodiments.

As noted above, the stimulating assembly 118 is inserted into therecipient's scala tympani 250. The scala tympani 250 is substantiallyfilled with a conductive fluid known as perilymph. As such, when currentsignals are delivered at one of the intra-cochlear contacts, at least aportion of the current will spread through the perilymph. For example,as shown in FIGS. 2A-2C, following delivery of current signals atcontact 128(22), the conductive nature of the perilymph will cause atleast some current to flow away from the contact in the generaldirections illustrated by arrows 254(A) and 254(B). The flow of thecurrent through the perilymph will cause the generation of voltages atthe other intra-cochlear stimulating contacts. That is, although thestimulus is localized, due to the conductive perilymph the electricfield spreads and induces voltage at the other contacts.

At 304, following the delivery of the current signals at contact128(22), voltage measurements are performed at a selected number ofother intra-cochlear contacts. That is, the voltage induced at theselected other contacts as a result of the delivery of the currentsignals at contact 128(22) is measured. The contacts at which thevoltages are measured are sometimes referred to herein as “measurement”contacts. In the embodiment of FIG. 3, the measurement contacts mayinclude any of the contacts 128(1)-128(22).

In certain circumstances, the cochlear implant 100 associated withstimulating assembly 118 is configured to make a plurality of voltagemeasurements at substantially the same time in response to the deliveryof stimulation. In such embodiments, a single set of localized currentsignals is applied and the voltage induced at a selected number of themeasurement contacts is measured substantially simultaneously at themeasurement contacts. In other embodiments, the cochlear implant 100 isconfigured to measure the voltage at a single contact in response to thedelivery of a set of current signals. In such embodiments, a pluralityof sets of localized current signals are applied in sequence at contact128(22), and a voltage is measured at a different contact after eachsequential stimulation. As such, in the context of FIG. 3, the deliveryof single stimulation pattern may refer to the delivery of one set ofcurrent signals (with subsequent substantially simultaneous measurementat each of the selected measurement contacts) or the sequential deliveryof plurality of sets of current signals (with subsequent measurement atone of the selected measurement contacts after each set of currentsignals are delivered).

As noted above, stimulation delivered at a contact will have an effecton the other contacts, and the effect may depend on a number of factors.However, a primary factor that controls the effects of stimulation isthe distance between the stimulating contact and the measurementcontact. For example, in the embodiment of FIG. 3, when stimulation isdelivered at contact 128(22), the voltage measured at other contactsshould be increasingly smaller for contacts positioned farther from thestimulating contact 128(22). Therefore, at 306 of FIG. 3 the inducedvoltages measured at each of the measurement contacts in response to thesingle stimulation pattern are evaluated relative to one another todetermine the relative distance between the stimulating contact 228(22)and each of the measurement contacts (i.e., the contacts at whichvoltages are measured). As described further below with reference toFIGS. 4A-4C, evaluation of the voltages relative to one another enablesthe determination of the physical state of the stimulating assembly 118.Also as described further below, based on the evaluation of measurementsrelative to one another, the cochlear implant 100 or a connected devicemay generate feedback to a surgeon or other user that providesinformation about the physical state of the stimulating assembly 118and/or the occurrence of an adverse event.

FIG. 4A is a graph 460(A) that illustrates the voltages measured duringexecution of the localized monitoring method 300 during a typical normalinsertion (i.e., where no adverse events occur) in accordance with oneembodiment. The graph 460(A) has a vertical (Y) axis that represents themeasured voltage and a horizontal (X) axis that represents the selectedmeasurement contacts 128(1)-128(21). The selected measurement contacts128(1)-128(21) are shown on the horizontal axis in decreasing order(i.e., starting with measurement contact 128(21) closest to thestimulating contact 128(22)).

As noted, the stimulation is delivered at contact 128(22) and, as such,the measured voltage is highest at the measurement contact 128(21) thatis positioned closest to stimulating contact 128(22). As shown in FIG.4A, the voltage measured at each subsequent measurement contactdecreases with increasing distance from the stimulating contact 128(22).That is, the measured voltages graphically appear as a decay curve462(A), with the maximum recorded voltage occurring at the measurementcontact 128(21) adjacent to the stimulating contact 128(22), and theminimum recorded voltage occurring at the most proximal measurementcontact 128(1).

In contrast to FIG. 4A, FIG. 4B is a graph 460(B) that illustrates thevoltages measured during execution of the localized monitoring method300 during an insertion where an adverse event in the form of tipfoldover, as shown in FIG. 2B, occurs. Similar to FIG. 4A, the graph460(B) has a vertical axis that represents the measured voltage and ahorizontal axis that represents the selected measurement contacts128(1)-128(21). The selected measurement contacts 128(1)-128(21) areagain shown on the horizontal axis in decreasing order.

As noted, the stimulus is delivered at contact 128(22) and, as such, themeasured voltage is highest at the measurement contact 128(21) that ispositioned closest to stimulating contact 128(22). As shown in FIG. 4B,the voltage measured at each subsequent measurement contact generallydecreases with increasing distance from the stimulating contact 128(22).That is, the measured voltages graphically appear as a decay curve462(B), with the maximum recorded voltage occurring at the measurementcontact 128(21) adjacent to the stimulating contact 128(22), and theminimum recorded voltage occurring at the most proximal measurementcontact 128(1).

However, unlike the example of FIG. 4A, the decay curve 462(B) includesan abnormal/irregular region 464(B) that does not comply with thegenerally decreasing trend of FIG. 4A. The irregular region 464(B) ofFIG. 4B is a voltage peak that indicates an increase in the voltagemeasured at contact 128(15). More specifically, the measured voltagegenerally decreases from measurement contact 128(20) through measurementcontact 128(18). The measured voltage increases from measurement contact128(18) through 128(15), then decreases from measurement contact 128(15)through 128(1). The voltage increase from measurement contact 128(18)through 128(15), and the voltage peak at measurement contact 128(15),indicates that measurement contact 128(15) is located physically closerto the stimulating contact 128(22) than at least measurement contacts128(18) through 128(16) (and possibly other stimulating contacts). Asnoted above, this physical proximity between measurement contact 128(15)and the stimulating contact 128(22) is improper, indicating theoccurrence of an adverse event. The specific shape of the irregularregion 464(B) (i.e., a voltage peak with generally decreasing voltage oneither side of the peak) indicates tip foldover.

FIG. 4C is a graph 460(C) that illustrates the voltages measured duringexecution of the localized monitoring method 300 during an insertionwhere another adverse event in the form of deformation, as shown in FIG.2C, occurs. Similar to FIG. 4A, the graph 460(C) has a vertical axisthat represents the measured voltage and a horizontal axis thatrepresents the selected measurement contacts 128(1)-128(21). Theselected measurement contacts 128(1)-128(21) are again shown on thehorizontal axis in decreasing order.

As noted, stimulation is delivered at contact 128(22) and, as such, themeasured voltage is highest at the measurement contact 128(21) that ispositioned closest to stimulating contact 128(22). As shown in FIG. 4C,the voltage measured at each subsequent measurement contact generallydecreases with increasing distance from the stimulating contact. Thatis, the measured voltages graphically appear as a decay curve 462(C),with the maximum recorded voltage occurring at the measurement contact128(21) adjacent to the stimulating contact 128(21), and the minimumrecorded voltage occurring at the most proximal measurement contact128(1).

However, unlike the example of FIG. 4A, the decay curve 462(C) includesan abnormal/irregular region 464(C) that does not comply with thegenerally decreasing trend of FIG. 4A. The irregular region 464(C) ofFIG. 4C is a generally flattened/tiered region indicating that thevoltage measured at a plurality of measurement contacts is substantiallythe same. More specifically, the measured voltage generally decreasesfrom measurement contact 128(20) through measurement contact 128(14).However, the voltage measured at measurement contacts 128(13) through128(8) is substantially the same with only a minor drop at measurementcontact 128(11). The measured voltage then decreases from measurementcontact 128(7) through 128(1). The generally flattened/tiered region464(C) indicates that measurement contacts 128(13) through 128(8) areall generally located substantially the same physical distance from thestimulating contact 128(22). This substantially same physical distancebetween measurement contacts 128(13) through 128(8) and the stimulatingcontact 128(22) is improper, indicating the occurrence of an adverseevent. The specific shape of the irregular region 464(C) (i.e., agenerally flattened region) indicates deformation at the region ofmeasurement contacts 128(13) through 128(8).

The embodiments of FIGS. 3 and 4A-4C have been described with referenceto the use of the two most distal contacts for delivering the localizedstimulation. It is to be appreciated that the use of the two most distalcontacts is illustrative and that other contacts may be used to deliverlocalized stimulation. For example, in one alternative embodiment, othercontacts within distal region 237, such as contacts 128(21) or 120(20)could be used as the stimulating contact or the return contact. Inanother alternative arrangement, contacts 128(15) and 128(16), locatedwithin the mid-region of the stimulating assembly 118 may be used todeliver localized stimulation. Such embodiments may be used alone (e.g.,if the distal contact and/or associated wire is broken), or incombination with the illustrative embodiment of FIG. 3 (e.g., as aconfirmation mechanism).

The embodiments of FIGS. 3 and 4A-4C have also been described withreference to measurement of voltage values at the measurement contacts.Other embodiments may deliver localized stimulation in the same manneras described above, but then measure the impedance at the measurementcontacts. The impedance measurements could then be used to determine thephysical state of the stimulating assembly.

In summary, FIGS. 3 and 4A-4C illustrate localized monitoring techniqueswhere stimulation occurs between two contacts and electrical parameters(e.g., voltage or impedance) are taken from consecutive contacts alongthe stimulating assembly. The electrical measurements are evaluatedrelative to one another to determine relative distances and thusdetermine the physical state/location of the stimulating assembly,thereby enabling the detection of adverse events.

FIG. 5 is a flowchart of another method 500 for monitoring the physicalstate of the stimulating assembly through the use of bipolarstimulation. As such, the method 500 of FIG. 5 is sometimes referred toherein as a bipolar monitoring method. For ease of illustration, method500 will be described with reference to the cochlear implant 100 of FIG.1 and details of stimulating assembly 118 shown in FIGS. 2A-2C.

Method 500 begins at 502 where stimulation (i.e., one or more currentsignals) is delivered between a first intra-cochlear contact and asecond intra-cochlear contact. In one specific example, the stimulationis first delivered between the most distal/apical contact 128(22) and atthe second most distal contact 128(21) (i.e., the contact adjacent tocontact 128(22)). The contact that delivers the current signals, namelycontact 128(22), is sometimes referred to herein as the “stimulating” or“source” contact and the contact that sinks the current, namely contact128(21), is sometimes referred to herein as the “return” contact.Additionally, the two contacts between which the stimulation isdelivered (e.g., the two most distal/apical contacts) are collectivelyreferred to herein as a “stimulating pair.” The remaining contacts thatare not part of the stimulating pair are disconnected from the systemground (i.e., are electrically “floating”).

In general, two intra-cochlear contacts are selected for delivery of thebipolar stimulation. However, alternative embodiments may use anextra-cochlear contact to source/sink current.

At 504, following the delivery of the current signals between thestimulating contact 128(22) and the return contact 128(21), anelectrical measurement is performed at the return contact. For example,the voltage induced at the return contact 128(21) as a result of thedelivery of the current signals at contact 128(22) is measured. Since anelectrical measurement is performed at the return contact 128(21), thereturn contact is sometimes referred to herein as a “measurement”contact.

The bipolar monitoring method 500 utilizes a plurality of electricalmeasurements made at a selected number of different contacts todetermine a physical state of the stimulating assembly 118. As such,electrical measurements need to also be made at additional contacts(i.e., other than contact 128(21)). Accordingly, at 506, a determinationis made as to whether electrical measurements have been made at all of aselected number of the contacts. Similar to the embodiment of FIG. 3,the contacts at which measurements may be performed are sometimesreferred to herein as measurement contacts. Any of the contacts128(1)-128(22) may operate as measurement contacts as they may be usedto perform electrical measurements.

If it is determined at 506 that electrical measurements have not beenmade at all of the selected number of measurement contacts, then at 508another measurement contact is made the return contact of thestimulating pair. For example, contact 128(20) (i.e., the next contactin the contact array 126) may be made the return contact by electricallyconnecting the contact 128(20) to ground and disconnecting the previousreturn contact (i.e., contact 128(21)) from ground (i.e., so that theprevious return contact is electrically floating). As a result, thestimulating pair then comprises stimulating contact 128(22) andmeasurement contact 128(20).

After changing the return contact, method 500 returns to 502 wherestimulation is delivered between stimulating contact 128(22) and thereturn contact 128(20). At 504, following the delivery of the currentsignals between the stimulating contact 128(22) and the return contact128(20), an electrical measurement is performed at the return contact.Method 500 then returns to 506 for another determination of whetherelectrical measurements have been made at all of the selected number ofmeasurement contacts. The loop defined by 508, 502, 504, and 506continues until measurements are made at all of the selected measurementcontacts.

Once it is determined at 506 that measurements have been made at all ofthe selected measurement contacts, method 500 proceeds to 510 where theelectrical measurements are evaluated relative to one another todetermine the relative proximity between the stimulating contact 228(22)and each of the measurement contacts. As described further below withreference to FIGS. 5A-5C, evaluation of the measurements relative to oneanother enables the determination of the physical state of thestimulating assembly 118. Also as described further below, based on theevaluation of measurements relative to one another, the cochlear implant100 or a connected device may generate feedback to a surgeon or otheruser that provides information about the physical state of thestimulating assembly 118 and/or the occurrence of an adverse event.

FIG. 6A is a graph 660(A) that illustrates the voltages measured duringexecution of the bipolar monitoring method 500 during a typical normalinsertion (i.e., where no adverse events occur) in accordance with oneembodiment. The graph 660(A) has a vertical axis that representsmeasured bipolar voltages and a horizontal axis that represents theselected measurement contacts 128(1)-128(21). The selected measurementcontacts 128(1)-128(21) are shown on the horizontal axis in decreasingorder (i.e., starting with measurement contact 128(21) closest to thestimulating contact 128(22)).

For a properly inserted stimulating assembly, the measured bipolarvoltage increases towards the basal end of the stimulating assembly.That is, as the distance between the stimulating contact 128(22) and ameasurement contact increases, the bipolar voltage also increases.Therefore, as shown in FIG. 6A, the measured bipolar voltagesgraphically appear as a growth curve 662(A), with the minimum voltageoccurring at measurement contact 128(21) adjacent to the stimulatingcontact 128(22) and the maximum voltage occurring at the mostproximal/basal measurement contact 128(1).

FIG. 6B is a graph 660(B) that illustrates the bipolar voltages measuredduring execution of the bipolar monitoring method 500 during aninsertion where an adverse event in the form of tip foldover, as shownin FIG. 2B, occurs. Similar to FIG. 6A, the graph 660(B) has a verticalaxis that represents the measured bipolar voltage and a horizontal axisthat represents the selected measurement contacts 128(1)-128(21). Theselected measurement contacts 128(1)-128(21) are again shown on thehorizontal axis in decreasing order.

As shown in FIG. 6B, the measured bipolar voltage generally increases ateach subsequent measurement contact with increasing distance from thestimulating contact 128(22). That is, growth curve 662(B) illustratesthat as the distance between the stimulating contact 128(22) and ameasurement contact increases, the bipolar voltage also generallyincreases. However, unlike the example of FIG. 6A, the growth curve662(B) includes an abnormal/irregular region 664(B) that does not complywith the generally increasing trend of FIG. 6A. The irregular region664(B) of FIG. 6B is a voltage trough that indicates a decrease in thevoltage measured around contact 128(15). The voltage decrease aroundcontact 128(15) indicates that measurement contact 128(15) isunexpectedly located physically closer to the stimulating contact128(22). This physical proximity between measurement contact 128(15) andthe stimulating contact 128(22) is improper, indicating the occurrenceof an adverse event. The specific shape of the irregular region 664(B)(i.e., a voltage trough with voltage increases on either side of thetrough) indicates tip foldover.

FIG. 6C is a graph 660(C) that illustrates the bipolar voltages measuredduring execution of the bipolar monitoring method 500 during aninsertion where another adverse event in the form of deformation, asshown in FIG. 2C, occurs. Similar to FIG. 6A, the graph 660(C) has avertical axis that represents the measured bipolar voltage and ahorizontal axis that represents the selected measurement contacts128(1)-128(21). The selected measurement contacts 128(1)-128(21) areagain shown on the horizontal axis in decreasing order.

As shown in FIG. 6B, the measured bipolar voltage generally increases ateach subsequent measurement contact with increasing distance from thestimulating contact 128(22). That is, growth curve 662(B) illustratesthat as the distance between the stimulating contact 128(22) and ameasurement contact increases, the bipolar voltage also increases.However, unlike the example of FIG. 6A, the curve 662(C) includes anabnormal/irregular region 664(C) that does not comply with the generallyincreasing trend of FIG. 6A. The irregular region 664(C) of FIG. 6C is agenerally flattened/tiered region indicating that the voltage measuredat a plurality of measurement contacts is substantially the same. Morespecifically, the measured voltage generally increases from measurementcontact 128(21) through measurement contact 128(14). However, thevoltage measured at measurement contacts 128(13) through 128(8) issubstantially the same with only a minor increase at measurement contact128(11). The voltage then increases from measurement contact 128(7)through 128(1). The generally flattened/tiered region 664(C) indicatesthat measurement contacts 128(13) through 128(8) are all generallylocated substantially the same physical distance from the stimulatingcontact 128(22). This substantially same physical proximity betweenmeasurement contacts 128(13) through 128(8) and the stimulating contact128(22) is improper, indicating the occurrence of an adverse event. Thespecific shape of the irregular region 664(C) (i.e., a generallyflattened region) indicates deformation at the region of measurementcontacts 128(13) through 128(8).

The embodiments of FIGS. 6 and 6A-6C have also been described withreference to measurement of voltage values at the measurement contacts.Other embodiments may deliver bipolar stimulation in the same manner asdescribed above, but then measure the impedance at the measurementcontacts. The impedance measurements could then be used to determine thephysical state of the stimulating assembly.

In summary, FIGS. 5 and 6A-6C illustrate embodiments in which bipolarstimulation is delivered between one particular contact (i.e., thestimulating contact) and other contacts in the array in a sequentialmanner. Electrical parameters (e.g., voltage or impedance) taken fromthe return contacts are evaluated relative to one another to determinerelative distances and thus determine the physical state/location of thestimulating assembly, thereby enabling the detection of adverse events.

The results of the evaluation conducted in the localized or bipolarmonitoring methods can be presented as feedback to the surgeon or otheruser to provide an indication of the physical state of the stimulatingassembly. The feedback may take a number of different forms in order toeffectively portray the physical state information. For example, in oneembodiment, a graph of the electrical measurements may be visuallydisplayed to the surgeon. The surgeon, surgical assistant, etc. couldmonitor the graph for changes indicating an adverse event has occurredor is about to occur.

In another embodiment, other visual cues/feedback such as flashinglights, the display of an image of the estimated shape of thestimulating assembly, etc. may be used to indicate when an adverse eventhas occurred or is about to occur. For example, light emitting diodes(LEDs) on an external sound processor could be used to provide thevisual cues to the surgeon.

In other embodiments, audible cues such as beeps or tones may be used toindicate when an adverse event has occurred or is about to occur. Forexample, an audible warning may be generated if it is determined that anevent has occurred or is about to occur (e.g., an audible warning may begenerated when the tip of the stimulating assembly becomes stuck or hasbegun to contact or perforate the basilar membrane). In a furtherembodiment, haptic (tactile) cues may be used to indicate when anadverse event has occurred or is about to occur. For example, vibrationsor a buzzing may be generated if it is determined that an event hasoccurred or is about to occur. It is also to be appreciated thatdifferent types of feedback may be used in combination with one another(i.e., a visual presentation on a display screen along with an audiblewarning when an event has occurred or is about to occur).

FIG. 7 is a block diagram illustrating further details of cochlearimplant 700 configured for monitoring the physical state of astimulating assembly in accordance with embodiments presented herein.The cochlear implant 700 comprises an external component 702 and animplantable component 704.

The implantable component 704 is disposed beneath a recipient'sskin/tissue 755 and comprises an implant body 714 connected to theelongate stimulating assembly 718 via a lead region 716. The stimulatingassembly 718 comprises a plurality of contacts 728 forming a contactarray 726. For ease of illustration, only a subset of the contacts 728in contact array 726 is shown in FIG. 7. The implant body 714 comprisesa stimulator unit 720, a transceiver unit 724, and an implantable coil722.

The external component 702 may be, for example, a behind-the-ear device,body-worn sound processor, coil (button) processor, etc. The externalcomponent 702 comprises a user interface 768, one or more sound inputelements 708 (e.g., microphones, telecoils, etc.) for detecting sound,one or more processors 770 (e.g., including a sound processor), a powersource 771 (e.g., battery), a transceiver unit 772, an external coil706, and a memory 774. Memory 774 comprises measurement logic 775 andevaluation logic 776.

Memory 774 may comprise read only memory (ROM), random access memory(RAM), magnetic disk storage media devices, optical storage mediadevices, flash memory devices, electrical, optical, or otherphysical/tangible memory storage devices. One or more of the processors770 are, for example, a microprocessor or microcontroller that executesinstructions for the measurement logic 775 and evaluation logic 776.Thus, in general, the memory 774 may comprise one or more tangible(non-transitory) computer readable storage media (e.g., a memory device)encoded with software comprising computer executable instructions andwhen the software is executed (by a processor 770) it is operable toperform the operations described herein in connection with themonitoring methods described herein. More specifically, measurementlogic 775 may be executed by the processor 770 to generatesignals/commands that cause stimulator unit 720 to: (1) generatestimulation (i.e., localized stimulation or bipolar stimulation), and(2) obtain electrical measurements at the measurement contacts.Evaluation logic 776 may be executed by a processor 770 to evaluate themeasurements and generate feedback to a surgeon or other user. In theexample of FIG. 7, the processor 770 that executes the measurement logic775 and the evaluation logic 776 is sometimes referred to herein as anevent detection processor.

Measurements are obtained by the stimulator unit 720 from measurementcontacts 728(1)-728(21) as measurement signals 778. The measurementsignals 778 may be transmitted to external component 702 for processing.That is, transceiver unit 724 transmits the measurement signals 778 totransceiver unit 772 via implantable coil 722 and external coil 706.Once the measurement signals 778 are received at the external component702, the signals may be processed by processor 770 executing measurementlogic 775. A processor 770 may further execute evaluation logic 776 todetermine the physical state of stimulating assembly 718 and generatefeedback to a user.

In certain embodiments, the measurement signals 778 may be stored in thememory 774 prior to use by the processor 770. The measurement signals778 may be stored temporarily (e.g., during collection of measurementsand/or for use during processing) or semi-permanently (i.e., forsubsequent export to another device).

FIG. 7 illustrates an example in which cochlear implant 700 includes anexternal component 702 with an external sound processor. It is to beappreciated that the use of an external component is merely illustrativeand that the monitoring techniques presented herein may be used inarrangements having an implanted sound processor (e.g., totallyimplantable cochlear implants). It is also to be appreciated that theindividual components referenced herein, e.g., sound input elements 708and the sound processor, may be distributed across more than oneauditory prosthesis, e.g., two cochlear implants, and indeed across morethan one type of device, e.g., cochlear implant 700 and a consumerelectronic device or a remote control of the cochlear implant 700.

It is to be appreciated that the monitoring functionality may notnecessarily form part of the cochlear implant as shown in FIG. 7. Forexample, FIG. 8 is a block diagram of an alternative arrangement inwhich the monitoring functionality is part of a separate computingdevice 880. For ease of reference, the embodiment of FIG. 8 will bedescribed with reference to the implantation of implantable component704 of FIG. 7 into a recipient 881.

The computing device 880 is a computing device that comprises aplurality of interfaces/ports 882(1)-882(N), a memory 884, a processor886, a user interface 888, a display device (e.g., screen) 890, and anaudio device (e.g., speaker) 892. The memory 884 comprises measurementlogic 875 and evaluation logic 876.

The interfaces 882(1)-882(N) may comprise, for example, any combinationof network ports (e.g., Ethernet ports), wireless network interfaces,Universal Serial Bus (USB) ports, Institute of Electrical andElectronics Engineers (IEEE) 1394 interfaces, PS/2 ports, etc. In theexample of FIG. 8, interface 882(1) is connected to an external coil 806and/or an external device (not shown) in communication with the externalcoil. Interface 678(1) may be configured to communicate with theexternal coil 806 (or other device) via a wired or wireless connection(e.g., telemetry, Bluetooth, etc.).

Memory 884 may comprise ROM, RAM, magnetic disk storage media devices,optical storage media devices, flash memory devices, electrical,optical, or other physical/tangible memory storage devices. Theprocessor 886 is, for example, a microprocessor or microcontroller thatexecutes instructions for the measurement logic 875 and evaluation logic876. Thus, in general, the memory 884 may comprise one or more tangible(non-transitory) computer readable storage media (e.g., a memory device)encoded with software comprising computer executable instructions andwhen the software is executed (by processor 886) it is operable toperform the operations described herein in connection with themonitoring methods described herein. More specifically, measurementlogic 875 may be executed by the processor 886 to generatesignals/commands that cause stimulator unit 720 to: (1) generatestimulation (i.e., localized stimulation or bipolar stimulation), and(2) obtain electrical measurements at the measurement contacts.Evaluation logic 876 may be executed by the processor 886 to evaluatethe measurements and generate feedback to a surgeon or other user. Inthe example of FIG. 8, the processor 886 that executes the measurementlogic 875 and the evaluation logic 876 is sometimes referred to hereinas an event detection processor.

The computing device 880 may be any of a number of different hardwareplatforms configured to perform the monitoring techniques presentedherein. In one embodiment, the computing device 880 is a computer (e.g.,laptop computer, desktop computer, etc.) present within the operatingtheatre. In another embodiment, the computing device 880 is anintraoperative remote assistant. In a further embodiment, the computingdevice 880 is an off-the-shelf device, such as a mobile phone or tabletdevice, to which the measurement logic 875 and evaluation logic 876 isdownloaded as an application or program. In these various embodiments ofFIG. 8, both control of the measurements and the display/notification ofevaluation results occur through the computing device 880.

FIG. 9 is a flowchart of a method 900 for monitoring a stimulatingassembly comprising a plurality of longitudinally spaced contacts.Method 900 begins at 902 where electrical stimulation is deliveredbetween two or more of the contacts. At 904, electrical parameters aremeasured at a selected number of the plurality of contacts in responseto the delivered electrical stimulation. At 906, the measured electricalparameters are evaluated relative to one another to determine a physicalstate of the stimulating assembly

As detailed above, presented herein are techniques for real-time (e.g.,intraoperative) monitoring of a stimulating assembly to determine thephysical state of the stimulating assembly and thus detect adverseevents such as tip foldover or deformation. As described further below,the monitoring utilizes variations in electrical measurements such asimpedance and voltage. A real-time algorithm utilizes the electricalmeasurements to determine the state of the stimulating assembly in thecochlea and thus detect tip foldover and/or deformation. In certainembodiments, the event detection techniques presented herein providesurgeons with a real-time indication that an adverse event has occurred,thereby enabling the surgeon to correct the insertion. This may provideimproved confidence in the quality of the stimulating assemblyinsertion, reduce the need for revision surgery, and improve the hearingperformance outcomes of recipients. The techniques presented herein mayalso enable consistent insertions across substantially all recipients,making the insertion process more repeatable regardless of the surgeon'sexperience. Confirming the state of the stimulating assembly duringsurgery also reduces the need for post-operative imaging, translating tocost and time benefits for recipients and hospitals, and reducingrecipient exposure to radiation. Data obtained from each insertion mayalso be logged and could be used for traceability, trending or productdevelopment.

The monitoring techniques in accordance with embodiments of the presentinvention have been primarily described with reference to the deliveryof bipolar stimulation to detect various adverse events. It is to beappreciated that other embodiments of the monitoring techniques may usemultipolar stimulation patterns (e.g., current steering, current/voltageshaping/focussing, etc.) to detect adverse events

The monitoring techniques presented herein may provide one or morebenefits to recipients, surgeons, or other users. In particular, themonitoring techniques may provide surgeons with a method for determiningthe state of the stimulating at the time the insertion is performed.This allows the insertion to be corrected immediately if an adverseevent has occurred. Confirming the physical state of the stimulatingassembly during surgery also reduces the need for post-operativeimaging. This translates to cost and time benefits for recipients andhospitals, and reduces recipient exposure to radiation, which istypically associated with current post-operative imaging techniques.

Preventing the occurrence of an adverse event also reduces the risk oftrauma inflicted on the soft tissue structures of the cochlea.Furthermore, monitoring stimulating assembly insertion in real-time andbeing able to respond accordingly to adverse events also offers improvedconfidence in the quality of the insertion. This reduces the need forrevision surgery, improves the hearing performance outcomes of ourrecipients and ultimately provides recipients with a better, smoothercochlear implant experience. In addition, the proposed invention enablesconsistent insertions to be performed across all recipients, making theinsertion more repeatable regardless of the surgeon's level ofexperience and training.

It is to be appreciated that the above embodiments are not mutuallyexclusive and may be combined with one another in various arrangements.

The invention described and claimed herein is not to be limited in scopeby the specific preferred embodiments herein disclosed, since theseembodiments are intended as illustrations, and not limitations, ofseveral aspects of the invention. Any equivalent embodiments areintended to be within the scope of this invention. Indeed, variousmodifications of the invention in addition to those shown and describedherein will become apparent to those skilled in the art from theforegoing description. Such modifications are also intended to fallwithin the scope of the appended claims.

What is claimed is:
 1. One or more non-transitory computer readablestorage media encoded with instructions that, when executed by aprocessor, cause the processor to: source current via at least oneextra-cochlear electrode of an implantable medical device; sink thesourced current via at least one of a plurality of longitudinally spacedelectrodes of a stimulating assembly configured to implanted in acochlear of a recipient of the implantable medical device; reverse apolarity of the sourced current; following reversal of the polarity ofthe sourced current, measure a voltage at each of a number of theplurality of electrodes of the stimulating assembly; collect thevoltages measured at each of a number of the plurality of electrodes ofthe stimulating assembly to generate one or more voltage sets; andanalyze relative magnitudes of the one or more voltage sets to detect atleast one of a fold or a buckle in the stimulating assembly.
 2. Thecomputer readable storage media of claim 1, wherein the instructionsoperable to measure a voltage at each of a number of the plurality ofelectrodes of the stimulating assembly comprise instructions that, whenexecuted by the processor, cause the processor to: substantiallyconcurrently measure the voltage at each of the number of the pluralityof electrodes.
 3. The computer readable storage media of claim 1,wherein the instructions operable to measure a voltage at each of anumber of the plurality of electrodes of the stimulating assemblycomprise instructions that, when executed by the processor, cause theprocessor to: sequentially measure the voltage at each of the number ofthe plurality of electrodes.
 4. The computer readable storage media ofclaim 1, wherein the instructions operable to measure a voltage at eachof a number of the plurality of electrodes of the stimulating assemblycomprise instructions that, when executed by the processor, cause theprocessor to: measure the voltage at each electrode of the of thestimulating assembly except the at least one of the plurality ofelectrodes sinking the current sourced via the at least oneextra-cochlear electrode.
 5. The computer readable storage media ofclaim 1, wherein the instructions operable to measure a voltage at eachof a number of the plurality of electrodes of the stimulating assemblycomprise instructions that, when executed by the processor, cause theprocessor to: disconnect electrodes not sourcing or sinking current froma system ground.
 6. The computer readable storage media of claim 1,wherein the instructions operable to analyze relative magnitudes of theone or more voltage sets to detect at least one of a fold or buckle inthe stimulating assembly comprise instructions that, when executed bythe processor, cause the processor to: analyze the relative magnitudesof the voltages to determine a location of the at least one of a fold orbuckle the stimulating assembly.
 7. The computer readable storage mediaof claim 1, wherein the instructions operable to analyze relativemagnitudes of the one or more voltage sets to detect at least one of afold or buckle in the stimulating assembly comprise instructions that,when executed by the processor, cause the processor to: detect at leastone of a local maximum or a global maximum in the relative magnitudes ofthe voltages indicative of a presence of a fold in the stimulatingassembly.
 8. The computer readable storage media of claim 1, furthercomprising instructions that, when executed by the processor, cause theprocessor to: generate feedback to a user that indicates a presence ofthe at least one of a fold or buckle in the stimulating assembly.
 9. Thecomputer readable storage media of claim 8, wherein the instructionsoperable to generate feedback to a user that indicates the presence ofthe at least one of a fold or buckle in the stimulating assemblycomprise instructions that, when executed by the processor, cause theprocessor to: display an image of an estimated shape of the stimulatingassembly at a display screen.
 10. The computer readable storage media ofclaim 1, further comprising instructions that, when executed by theprocessor, cause the processor to: iteratively source current via atleast one extra-cochlear electrode; in response to each iteration ofcurrent sourced via the at least one extra-cochlear electrode,sequentially sink the sourced current via at least one of the pluralityof electrodes of the stimulating assembly; in response to each iterationof current sourced via the at least one extra-cochlear electrode,reverse the polarity of the sourced current; following reversal of thepolarity of the sourced current at each iteration, measure a voltage ateach of a number of the plurality of electrodes of the stimulatingassembly; collect the voltages measured at each of a number of theplurality of electrodes of the stimulating assembly to generate aplurality of voltage sets; and analyze relative magnitudes of thevoltages within the plurality of voltage sets to detect the at least oneof the fold or the buckle in the stimulating assembly.
 11. A method,comprising: at least partially inserting a stimulating assembly into acochlea of a recipient of an implantable medical device, wherein thestimulating assembly comprises a plurality of electrodes; iterativelysourcing current via at least one remote electrode of the implantablemedical device, wherein the at least one remote electrode is configuredto be implanted in the recipient and is electrical distant from theplurality of electrodes of the stimulating assembly; in response to eachiteration of current sourced via the at least one remote electrode,sequentially sinking the sourced current via at least one of theplurality of electrodes of the stimulating assembly; in response to eachiteration of current sourced via the at least one remote electrode,reversing a polarity of the sourced current; following reversal of thepolarity of the sourced current at each iteration, measuring a voltageat each of a number of the plurality of electrodes of the stimulatingassembly; collecting the voltages measured at each of a number of theplurality of electrodes of the stimulating assembly to generate aplurality of voltage sets; and analyzing relative magnitudes of thevoltages within the plurality of voltage sets to detect the at least oneof a fold or a buckle in the stimulating assembly.
 12. The method ofclaim 11, wherein measuring a voltage at each of a number of theplurality of electrodes of the stimulating assembly comprises:substantially concurrently measuring the voltage at each of the numberof the plurality of electrodes.
 13. The method of claim 11, whereinmeasuring a voltage at each of a number of the plurality of electrodesof the stimulating assembly comprises: sequentially measuring thevoltage at each of the number of the plurality of electrodes.
 14. Themethod of claim 11, wherein measuring a voltage at each of a number ofthe plurality of electrodes of the stimulating assembly comprises:measuring the voltage at each electrode of the of the stimulatingassembly except the at least one of the plurality of electrodes sinkingthe current sourced via the at least one remote electrode.
 15. Themethod of claim 11, wherein the at least one remote electrode is anextra-cochlear electrode.
 16. The method of claim 11, wherein analyzingthe relative magnitudes of the voltages within the plurality of voltagesets to detect the at least one of a fold or buckle in the stimulatingassembly further comprises: analyzing the relative magnitudes of thevoltages to determine a location of the at least one of a fold or bucklethe stimulating assembly.
 17. The method of claim 11, wherein analyzingthe relative magnitudes of the voltages within the plurality of voltagesets to detect the at least one of a fold or buckle in the stimulatingassembly further comprises: detecting a global maximum and a localmaximum in the relative magnitudes of the voltages indicative of apresence of a fold in the stimulating assembly.
 18. The method of claim11, further comprising: generating feedback to a user that indicates apresence of the at least one of a fold or buckle in the stimulatingassembly.
 19. The method of claim 19, wherein generating feedback to auser that indicates the presence of the at least one of a fold or bucklein the stimulating assembly comprises: displaying an image of anestimated shape of the stimulating assembly at a display screen.
 20. Themethod of claim 11, further comprising: determining, based on therelative magnitudes of the voltages within the plurality of voltagesets, a relative proximity of each electrode of the stimulating assemblyto one another; and estimating a shape of the stimulating assembly basedon the relative proximity of each electrode of the stimulating assemblyto one another.
 21. The method of claim 21, further comprising:displaying an image of the estimated shape of the stimulating assemblyat a display screen.